thodg/libgit2

diff --git a/src/regexp.c b/src/regexp.c
new file mode 100644
index 0000000..05ed190
--- /dev/null
+++ b/src/regexp.c
@@ -0,0 +1,221 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "regexp.h"
+
+#if defined(GIT_REGEX_BUILTIN) || defined(GIT_REGEX_PCRE)
+
+int git_regexp_compile(git_regexp *r, const char *pattern, int flags)
+{
+	int erroffset, cflags = 0;
+	const char *error;
+
+	if (flags & GIT_REGEXP_ICASE)
+		cflags |= PCRE_CASELESS;
+
+	if ((*r = pcre_compile(pattern, cflags, &error, &erroffset, NULL)) == NULL) {
+		git_error_set_str(GIT_ERROR_REGEX, error);
+		return GIT_EINVALIDSPEC;
+	}
+
+	return 0;
+}
+
+void git_regexp_dispose(git_regexp *r)
+{
+	pcre_free(*r);
+	*r = NULL;
+}
+
+int git_regexp_match(const git_regexp *r, const char *string)
+{
+	int error;
+	if ((error = pcre_exec(*r, NULL, string, (int) strlen(string), 0, 0, NULL, 0)) < 0)
+		return (error == PCRE_ERROR_NOMATCH) ? GIT_ENOTFOUND : GIT_EINVALIDSPEC;
+	return 0;
+}
+
+int git_regexp_search(const git_regexp *r, const char *string, size_t nmatches, git_regmatch *matches)
+{
+	int static_ovec[9], *ovec;
+	int error;
+	size_t i;
+
+	/* The ovec array always needs to be a mutiple of three */
+	if (nmatches <= ARRAY_SIZE(static_ovec) / 3)
+		ovec = static_ovec;
+	else
+		ovec = git__calloc(nmatches * 3, sizeof(*ovec));
+	GIT_ERROR_CHECK_ALLOC(ovec);
+
+	if ((error = pcre_exec(*r, NULL, string, (int) strlen(string), 0, 0, ovec, (int) nmatches * 3)) < 0)
+		goto out;
+
+	if (error == 0)
+		error = (int) nmatches;
+
+	for (i = 0; i < (unsigned int) error; i++) {
+		matches[i].start = (ovec[i * 2] < 0) ? -1 : ovec[i * 2];
+		matches[i].end = (ovec[i * 2 + 1] < 0) ? -1 : ovec[i * 2 + 1];
+	}
+	for (i = (unsigned int) error; i < nmatches; i++)
+		matches[i].start = matches[i].end = -1;
+
+out:
+	if (nmatches > ARRAY_SIZE(static_ovec) / 3)
+		git__free(ovec);
+	if (error < 0)
+		return (error == PCRE_ERROR_NOMATCH) ? GIT_ENOTFOUND : GIT_EINVALIDSPEC;
+	return 0;
+}
+
+#elif defined(GIT_REGEX_PCRE2)
+
+int git_regexp_compile(git_regexp *r, const char *pattern, int flags)
+{
+	unsigned char errmsg[1024];
+	unsigned long erroff;
+	int error, cflags = 0;
+
+	if (flags & GIT_REGEXP_ICASE)
+		cflags |= PCRE2_CASELESS;
+
+	if ((*r = pcre2_compile((const unsigned char *) pattern, PCRE2_ZERO_TERMINATED,
+				cflags, &error, &erroff, NULL)) == NULL) {
+		pcre2_get_error_message(error, errmsg, sizeof(errmsg));
+		git_error_set_str(GIT_ERROR_REGEX, (char *) errmsg);
+		return GIT_EINVALIDSPEC;
+	}
+
+	return 0;
+}
+
+void git_regexp_dispose(git_regexp *r)
+{
+	pcre2_code_free(*r);
+	*r = NULL;
+}
+
+int git_regexp_match(const git_regexp *r, const char *string)
+{
+	pcre2_match_data *data;
+	int error;
+
+	data = pcre2_match_data_create(1, NULL);
+	GIT_ERROR_CHECK_ALLOC(data);
+
+	if ((error = pcre2_match(*r, (const unsigned char *) string, strlen(string),
+			 0, 0, data, NULL)) < 0)
+		return (error == PCRE2_ERROR_NOMATCH) ? GIT_ENOTFOUND : GIT_EINVALIDSPEC;
+
+	pcre2_match_data_free(data);
+	return 0;
+}
+
+int git_regexp_search(const git_regexp *r, const char *string, size_t nmatches, git_regmatch *matches)
+{
+	pcre2_match_data *data = NULL;
+	PCRE2_SIZE *ovec;
+	int error;
+	size_t i;
+
+	if ((data = pcre2_match_data_create(nmatches, NULL)) == NULL) {
+		git_error_set_oom();
+		goto out;
+	}
+
+	if ((error = pcre2_match(*r, (const unsigned char *) string, strlen(string),
+			     0, 0, data, NULL)) < 0)
+		goto out;
+
+	if (error == 0 || (unsigned int) error  > nmatches)
+		error = nmatches;
+	ovec = pcre2_get_ovector_pointer(data);
+
+	for (i = 0; i < (unsigned int) error; i++) {
+		matches[i].start = (ovec[i * 2] == PCRE2_UNSET) ? -1 : (ssize_t) ovec[i * 2];
+		matches[i].end = (ovec[i * 2 + 1] == PCRE2_UNSET) ? -1 :  (ssize_t) ovec[i * 2 + 1];
+	}
+	for (i = (unsigned int) error; i < nmatches; i++)
+		matches[i].start = matches[i].end = -1;
+
+out:
+	pcre2_match_data_free(data);
+	if (error < 0)
+		return (error == PCRE2_ERROR_NOMATCH) ? GIT_ENOTFOUND : GIT_EINVALIDSPEC;
+	return 0;
+}
+
+#elif defined(GIT_REGEX_REGCOMP) || defined(GIT_REGEX_REGCOMP_L)
+
+#if defined(GIT_REGEX_REGCOMP_L)
+# include <xlocale.h>
+#endif
+
+int git_regexp_compile(git_regexp *r, const char *pattern, int flags)
+{
+	int cflags = REG_EXTENDED, error;
+	char errmsg[1024];
+
+	if (flags & GIT_REGEXP_ICASE)
+		cflags |= REG_ICASE;
+
+# if defined(GIT_REGEX_REGCOMP)
+	if ((error = regcomp(r, pattern, cflags)) != 0)
+# else
+	if ((error = regcomp_l(r, pattern, cflags, (locale_t) 0)) != 0)
+# endif
+	{
+		regerror(error, r, errmsg, sizeof(errmsg));
+		git_error_set_str(GIT_ERROR_REGEX, errmsg);
+		return GIT_EINVALIDSPEC;
+	}
+
+	return 0;
+}
+
+void git_regexp_dispose(git_regexp *r)
+{
+	regfree(r);
+}
+
+int git_regexp_match(const git_regexp *r, const char *string)
+{
+	int error;
+	if ((error = regexec(r, string, 0, NULL, 0)) != 0)
+		return (error == REG_NOMATCH) ? GIT_ENOTFOUND : GIT_EINVALIDSPEC;
+	return 0;
+}
+
+int git_regexp_search(const git_regexp *r, const char *string, size_t nmatches, git_regmatch *matches)
+{
+	regmatch_t static_m[3], *m;
+	int error;
+	size_t i;
+
+	if (nmatches <= ARRAY_SIZE(static_m))
+		m = static_m;
+	else
+		m = git__calloc(nmatches, sizeof(*m));
+
+	if ((error = regexec(r, string, nmatches, m, 0)) != 0)
+		goto out;
+
+	for (i = 0; i < nmatches; i++) {
+		matches[i].start = (m[i].rm_so < 0) ? -1 : m[i].rm_so;
+		matches[i].end = (m[i].rm_eo < 0) ? -1 : m[i].rm_eo;
+	}
+
+out:
+	if (nmatches > ARRAY_SIZE(static_m))
+		git__free(m);
+	if (error)
+		return (error == REG_NOMATCH) ? GIT_ENOTFOUND : GIT_EINVALIDSPEC;
+	return 0;
+}
+
+#endif
diff --git a/src/regexp.h b/src/regexp.h
new file mode 100644
index 0000000..2592ef3
--- /dev/null
+++ b/src/regexp.h
@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#ifndef INCLUDE_regexp_h__
+#define INCLUDE_regexp_h__
+
+#include "common.h"
+
+#if defined(GIT_REGEX_BUILTIN) || defined(GIT_REGEX_PCRE)
+# include "pcre.h"
+typedef pcre *git_regexp;
+# define GIT_REGEX_INIT NULL
+#elif defined(GIT_REGEX_PCRE2)
+# define PCRE2_CODE_UNIT_WIDTH 8
+# include <pcre2.h>
+typedef pcre2_code *git_regexp;
+# define GIT_REGEX_INIT NULL
+#elif defined(GIT_REGEX_REGCOMP) || defined(GIT_REGEX_REGCOMP_L)
+# include <regex.h>
+typedef regex_t git_regexp;
+# define GIT_REGEX_INIT { 0 }
+#else
+# error "No regex backend"
+#endif
+
+/** Options supported by @git_regexp_compile. */
+typedef enum {
+	/** Enable case-insensitive matching */
+	GIT_REGEXP_ICASE = (1 << 0)
+} git_regexp_flags_t;
+
+/** Structure containing information about regular expression matching groups */
+typedef struct {
+	/** Start of the given match. -1 if the group didn't match anything */
+	ssize_t start;
+	/** End of the given match. -1 if the group didn't match anything */
+	ssize_t end;
+} git_regmatch;
+
+/**
+ * Compile a regular expression. The compiled expression needs to
+ * be cleaned up afterwards with `git_regexp_dispose`.
+ *
+ * @param r Pointer to the storage where to initialize the regular expression.
+ * @param pattern The pattern that shall be compiled.
+ * @param flags Flags to alter how the pattern shall be handled.
+ *              0 for defaults, otherwise see @git_regexp_flags_t.
+ * @return 0 on success, otherwise a negative return value.
+ */
+int git_regexp_compile(git_regexp *r, const char *pattern, int flags);
+
+/**
+ * Free memory associated with the regular expression
+ *
+ * @param r The regular expression structure to dispose.
+ */
+void git_regexp_dispose(git_regexp *r);
+
+/**
+ * Test whether a given string matches a compiled regular
+ * expression.
+ *
+ * @param r Compiled regular expression.
+ * @param string String to match against the regular expression.
+ * @return 0 if the string matches, a negative error code
+ *         otherwise. GIT_ENOTFOUND if no match was found,
+ *         GIT_EINVALIDSPEC if the regular expression matching
+ *         was invalid.
+ */
+int git_regexp_match(const git_regexp *r, const char *string);
+
+/**
+ * Search for matches inside of a given string.
+ *
+ * Given a regular expression with capturing groups, this
+ * function will populate provided @git_regmatch structures with
+ * offsets for each of the given matches. Non-matching groups
+ * will have start and end values of the respective @git_regmatch
+ * structure set to -1.
+ *
+ * @param r Compiled regular expression.
+ * @param string String to match against the regular expression.
+ * @param nmatches Number of @git_regmatch structures provided by
+ *                 the user.
+ * @param matches Pointer to an array of @git_regmatch structures.
+ * @return 0 if the string matches, a negative error code
+ *         otherwise. GIT_ENOTFOUND if no match was found,
+ *         GIT_EINVALIDSPEC if the regular expression matching
+ *         was invalid.
+ */
+int git_regexp_search(const git_regexp *r, const char *string, size_t nmatches, git_regmatch *matches);
+
+#endif
diff --git a/tests/core/regexp.c b/tests/core/regexp.c
new file mode 100644
index 0000000..8db5641
--- /dev/null
+++ b/tests/core/regexp.c
@@ -0,0 +1,213 @@
+#include "clar_libgit2.h"
+
+#include <locale.h>
+
+#include "regexp.h"
+#include "userdiff.h"
+
+#if LC_ALL > 0
+static const char *old_locales[LC_ALL];
+#endif
+
+static git_regexp regex;
+
+void test_core_regexp__initialize(void)
+{
+#if LC_ALL > 0
+	memset(&old_locales, 0, sizeof(old_locales));
+#endif
+}
+
+void test_core_regexp__cleanup(void)
+{
+	git_regexp_dispose(&regex);
+}
+
+static void try_set_locale(int category)
+{
+#if LC_ALL > 0
+	old_locales[category] = setlocale(category, NULL);
+#endif
+
+	if (!setlocale(category, "UTF-8") &&
+	    !setlocale(category, "c.utf8") &&
+	    !setlocale(category, "en_US.UTF-8"))
+		cl_skip();
+
+	if (MB_CUR_MAX == 1)
+		cl_fail("Expected locale to be switched to multibyte");
+}
+
+
+void test_core_regexp__compile_ignores_global_locale_ctype(void)
+{
+	try_set_locale(LC_CTYPE);
+	cl_git_pass(git_regexp_compile(&regex, "[\xc0-\xff][\x80-\xbf]", 0));
+}
+
+void test_core_regexp__compile_ignores_global_locale_collate(void)
+{
+#ifdef GIT_WIN32
+	cl_skip();
+#endif
+
+	try_set_locale(LC_COLLATE);
+	cl_git_pass(git_regexp_compile(&regex, "[\xc0-\xff][\x80-\xbf]", 0));
+}
+
+void test_core_regexp__regex_matches_digits_with_locale(void)
+{
+	char c, str[2];
+
+#ifdef GIT_WIN32
+	cl_skip();
+#endif
+
+	try_set_locale(LC_COLLATE);
+	try_set_locale(LC_CTYPE);
+
+	cl_git_pass(git_regexp_compile(&regex, "[[:digit:]]", 0));
+
+	str[1] = '\0';
+	for (c = '0'; c <= '9'; c++) {
+	    str[0] = c;
+	    cl_git_pass(git_regexp_match(&regex, str));
+	}
+}
+
+void test_core_regexp__regex_matches_alphabet_with_locale(void)
+{
+	char c, str[2];
+
+#ifdef GIT_WIN32
+	cl_skip();
+#endif
+
+	try_set_locale(LC_COLLATE);
+	try_set_locale(LC_CTYPE);
+
+	cl_git_pass(git_regexp_compile(&regex, "[[:alpha:]]", 0));
+
+	str[1] = '\0';
+	for (c = 'a'; c <= 'z'; c++) {
+	    str[0] = c;
+	    cl_git_pass(git_regexp_match(&regex, str));
+	}
+	for (c = 'A'; c <= 'Z'; c++) {
+	    str[0] = c;
+	    cl_git_pass(git_regexp_match(&regex, str));
+	}
+}
+
+void test_core_regexp__compile_userdiff_regexps(void)
+{
+	size_t idx;
+
+	for (idx = 0; idx < ARRAY_SIZE(builtin_defs); ++idx) {
+		git_diff_driver_definition ddef = builtin_defs[idx];
+
+		cl_git_pass(git_regexp_compile(&regex, ddef.fns, ddef.flags));
+		git_regexp_dispose(&regex);
+
+		cl_git_pass(git_regexp_compile(&regex, ddef.words, 0));
+		git_regexp_dispose(&regex);
+	}
+}
+
+void test_core_regexp__simple_search_matches(void)
+{
+	cl_git_pass(git_regexp_compile(&regex, "a", 0));
+	cl_git_pass(git_regexp_search(&regex, "a", 0, NULL));
+}
+
+void test_core_regexp__case_insensitive_search_matches(void)
+{
+	cl_git_pass(git_regexp_compile(&regex, "a", GIT_REGEXP_ICASE));
+	cl_git_pass(git_regexp_search(&regex, "A", 0, NULL));
+}
+
+void test_core_regexp__nonmatching_search_returns_error(void)
+{
+	cl_git_pass(git_regexp_compile(&regex, "a", 0));
+	cl_git_fail(git_regexp_search(&regex, "b", 0, NULL));
+}
+
+void test_core_regexp__search_finds_complete_match(void)
+{
+	git_regmatch matches[1];
+
+	cl_git_pass(git_regexp_compile(&regex, "abc", 0));
+	cl_git_pass(git_regexp_search(&regex, "abc", 1, matches));
+	cl_assert_equal_i(matches[0].start, 0);
+	cl_assert_equal_i(matches[0].end, 3);
+}
+
+void test_core_regexp__search_finds_correct_offsets(void)
+{
+	git_regmatch matches[3];
+
+	cl_git_pass(git_regexp_compile(&regex, "(a*)(b*)", 0));
+	cl_git_pass(git_regexp_search(&regex, "ab", 3, matches));
+	cl_assert_equal_i(matches[0].start, 0);
+	cl_assert_equal_i(matches[0].end, 2);
+	cl_assert_equal_i(matches[1].start, 0);
+	cl_assert_equal_i(matches[1].end, 1);
+	cl_assert_equal_i(matches[2].start, 1);
+	cl_assert_equal_i(matches[2].end, 2);
+}
+
+void test_core_regexp__search_finds_empty_group(void)
+{
+	git_regmatch matches[3];
+
+	cl_git_pass(git_regexp_compile(&regex, "(a*)(b*)c", 0));
+	cl_git_pass(git_regexp_search(&regex, "ac", 3, matches));
+	cl_assert_equal_i(matches[0].start, 0);
+	cl_assert_equal_i(matches[0].end, 2);
+	cl_assert_equal_i(matches[1].start, 0);
+	cl_assert_equal_i(matches[1].end, 1);
+	cl_assert_equal_i(matches[2].start, 1);
+	cl_assert_equal_i(matches[2].end, 1);
+}
+
+void test_core_regexp__search_fills_matches_with_first_matching_groups(void)
+{
+	git_regmatch matches[2];
+
+	cl_git_pass(git_regexp_compile(&regex, "(a)(b)(c)", 0));
+	cl_git_pass(git_regexp_search(&regex, "abc", 2, matches));
+	cl_assert_equal_i(matches[0].start, 0);
+	cl_assert_equal_i(matches[0].end, 3);
+	cl_assert_equal_i(matches[1].start, 0);
+	cl_assert_equal_i(matches[1].end, 1);
+}
+
+void test_core_regexp__search_skips_nonmatching_group(void)
+{
+	git_regmatch matches[4];
+
+	cl_git_pass(git_regexp_compile(&regex, "(a)(b)?(c)", 0));
+	cl_git_pass(git_regexp_search(&regex, "ac", 4, matches));
+	cl_assert_equal_i(matches[0].start, 0);
+	cl_assert_equal_i(matches[0].end, 2);
+	cl_assert_equal_i(matches[1].start, 0);
+	cl_assert_equal_i(matches[1].end, 1);
+	cl_assert_equal_i(matches[2].start, -1);
+	cl_assert_equal_i(matches[2].end, -1);
+	cl_assert_equal_i(matches[3].start, 1);
+	cl_assert_equal_i(matches[3].end, 2);
+}
+
+void test_core_regexp__search_initializes_trailing_nonmatching_groups(void)
+{
+	git_regmatch matches[3];
+
+	cl_git_pass(git_regexp_compile(&regex, "(a)bc", 0));
+	cl_git_pass(git_regexp_search(&regex, "abc", 3, matches));
+	cl_assert_equal_i(matches[0].start, 0);
+	cl_assert_equal_i(matches[0].end, 3);
+	cl_assert_equal_i(matches[1].start, 0);
+	cl_assert_equal_i(matches[1].end, 1);
+	cl_assert_equal_i(matches[2].start, -1);
+	cl_assert_equal_i(matches[2].end, -1);
+}